This invention relates to self winding systems for timepieces and more particularly relates to temperature differential driven self-winding timepieces, particularly wristwatches, which are wound in response to change in temperature.
Many, if not all, wrist watches, other than battery powered watches, receive energy for winding a main spring through a main spring barrel arbor from a winding weight or rotor in the watch which rotates in a direction due to movement of the watch wearer's arm. This movement of the wearer's arm produces acceleration of the winding weight or rotor about a pivotal axis. This results in bi-directional rotation of the shaft upon which it is mounted. The bi-directional rotation of this shaft is converted to unidirectional rotation of another shaft, which in turn winds the mainspring. A simple and common mechanism for converting bi-directional rotation of one shaft in a watch to unidirectional rotation of another shaft is known as a Pellaton mechanism. A Pellaton mechanism comprises a lever, which is bifurcated at one end. The bifurcated arms are acted upon by a rotating cam or eccentric pin to produce an eccentric oscillating motion. Spring loaded pawls on the lever engage a ratchet wheel at spaced apart locations on the ratchet wheel causing unidirectional rotation of the ratchet with the oscillating motion of the lever induced by the winding weight or rotor, e.g. U.S. Pat. Nos. 2,696,073 and 4,174,607.
Another mechanism for this type of mechanical conversion is known as a wig-wag mechanism. Here, a pinion on a bi-directionally rotatable shaft drives a linearly displaceable wig-wag gear. This gear engages one of two other gears dependent on the direction of rotation of the wig-wag gear. The gear arrangement is organized such that the mainspring barrel will always be driven in a direction to wind the mainspring.
Self-winding wrist watches generally have a power reserve of about one and one-half to three days. This is also called autonomy. The terms “autonomy” and “power reserve” refer to the time a self winding wrist watch will continue to run if fully wound, but not worn. Various efforts to increase the power reserve of a watch have been undertaken, but still result in the watch losing all power reserve after a period of time of not being worn. Hence, there is a need for a self-winding watch that does not rely on its inherent power reserve derived from motion of a user's arm. The invention solves these and other needs in the art.